The structure of lanthanide-doped uranium dioxide, Ln xU 1-xO 2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO 2, such as Young's modulus.

@article{osti_1369255,
title = {Structure and bulk modulus of Ln-doped UO2 (Ln = La, Nd) at high pressure},
author = {Rittman, Dylan R. and Park, Sulgiye and Tracy, Cameron L. and Zhang, Lei and Palomares, Raul I. and Lang, Maik and Navrotsky, Alexandra and Mao, Wendy L. and Ewing, Rodney C.},
abstractNote = {The structure of lanthanide-doped uranium dioxide, LnxU1-xO2-0.5x+y (Ln = La, Nd), was investigated at pressures up to ~50–55 GPa. Samples were synthesized with different lanthanides at different concentrations (x ~ 0.2 and 0.5), and all were slightly hyperstoichiometric (y ~ 0.25–0.4). In situ high-pressure synchrotron X-ray diffraction was used to investigate their high-pressure phase behavior and determine their bulk moduli. All samples underwent a fluorite-to-cotunnite phase transformation with increasing pressure. The pressure of the phase transformation increased with increasing hyperstoichiometry, which is consistent with results from previous computational simulations. Bulk moduli are inversely proportional to both the ionic radius of the lanthanide and its concentration, as quantified using a weighted cationic radius ratio. As a result, this trend was found to be consistent with the behavior of other elastic properties measured for Ln-doped UO2, such as Young's modulus.},
doi = {10.1016/j.jnucmat.2017.04.007},
journal = {Journal of Nuclear Materials},
number = C,
volume = 490,
place = {United States},
year = {2017},
month = {4}
}

A large number of compounds which contain BiS 2 layers exhibit enhanced superconductivity upon electron doping. Much interest and research effort has been focused on BiS 2-based compounds which provide new opportunities for exploring the nature of superconductivity. Important to the study of BiS 2-based superconductors is the relation between structure and superconductivity. Furthermore, by modifying either the superconducting BiS 2 layers or the blocking layers in these layered compounds, one can effectively tune the lattice parameters, local atomic environment, electronic structure, and other physical properties of these materials. In our article, we will review some of the recent progressmore » on research of the effects of chemical substitution in BiS 2-based compounds, with special attention given to the compounds in the LnOBiS 2 (Ln = La-Nd) system. Finally, We discuss strategies which are reported to be essential in optimizing superconductivity of these materials.« less